Oberdorfer Pump Snap Ring - Official Answer

[jonelli]

I know there's been lots of discussion about using the impeller without the snap ring over the years. I've read a lot of the threads.
I also read that some believe it was just for shipping and you don't need it once it's installed on your boat.
I thought I'd ask them directly and see what I answer I got, but I've still been running mine without the ring anyway and has worked fine for the last couple of years.

Darin Mountain (OBERDORFER & MP Pumps) Mar 10, 2021, 15:34 CST The snap ring is needed in the pump assembly. IR/Oberdorfer does not recommend running the N202 series without all of the internal components in place. Darin Mountain Applications Specialist

 

[jonelli]

Although, I don't know if there's an extra risk of "spinning" it without the ring. Maybe there is?

 

[jonelli]

Well, I asked that as well, and this was the only answer:

"The snap ring insures proper alignment in the assembly."

 

[Stu Jackson]

That ring does nothing. The impeller isn't going anywhere. Just wait until Kloeber sees this one!

Why do some of our engines have different Oberdorfer sea water pumps than others, and what about that cir-clip "holding on the impeller"? - c34.org

c34.org

 

[weekendrken]

It’s bull cr@p. The guy doesn’t know what he’s saying.
You realize that “Oberdorfer” is no more - it was bought out long ago and moved?

PROOF:
The impeller is CAPTIVE in the water chamber. It CANNOT MOVE forward or backward.
BOTH SIDES of it hit - the cover one side and the back of the water chamber on the other.
Ok, take the impeller out of the discussion - it cannot move.

The ONLY thing that could possibly move is the shaft.
The shaft CANNOT move forward, the stop on the shaft where the flat ends, hits tight against the impeller. Therefore the shaft CANNOT move forward.
BESIDES, the snap ring wouldn’t stop the shaft from moving in THAT direction anyway.
Ok, take that movement/direction out of the discussion.

THEREFORE, the ring could stop the shaft from moving in ONLY ONE direction - AFT.
The shaft sits against the camshaft — so therefore it CANNOT move in the aft direction either.

He’s a dummy who can’t analyze a situation and regurgitates only the ‘corporate reply.’

Once installed in our engines, NOTHING in the pump can travel out of alignment, one way or the other, WITH or WITHOUT the ring.

Just wait till Stu sees this one.

The last part of this says it all:

Why do some of our engines have different Oberdorfer sea water pumps than others, and what about that cir-clip "holding on the impeller"? - c34.org

c34.org

 

[Stu Jackson]

Just wait until Kloeber sees this one!

Just wait till Stu sees this one.

Same link.
Great minds and all...
Beat ya!!! [by 8 minutes]

 

[stephen_i_w]

Without the snap ring I would imagine it might rub against the cover plate. Seems easy enough to keep it anyway.

 

[weekendrken]

@STEPHEN

What? The SHAFT rub against the cover?
NO, the shaft CANNOT hit the cover plate. IMPOSSIBLE. With or without the ring (am I repeating myself here?)

Or the IMPELLER?
It DOES rub against the cover plate, that's the design.
The ring DOES not prevent the impeller from moving -- the shaft and impeller would "float" (move) as one unit, so the ring prevents nothing at all relative to the impeller/water chamber. (Yes, I am repeating myself.)

Remember Murphy - if you overheat and time is critical (heading for a shoal or harbor) and need to pop in a new impeller in an emergency, would it be just as "easy enough" with the snap ring as it would be without it?
Crap, where did I stash my snap ring tool?


@Stu -- 8 mins, but only because it took 9 minutes for my analysis!!

 

[Alan Gomes]

The snap ring does one thing and one thing only: it keeps the shaft from sliding out the BACK of the pump. When the pump is actually installed on the engine, this can't happen. If the pump is off the engine for some reason, such as when it is being shipped somewhere, then it could. It serves zero purpose on an installed pump, and is simply an extra hassle to deal with when changing impellers.

In the past I have had two engines that used this pump and had absolutely no problems with running them minus the clip.

 

[stephen_i_w]

Wow, I had no idea how strongly people feel about this. Yes, OK, it does make sense that the impeller has to rub against the cover plate to maintain a seal. I have had boats with both Oberdorfer and Sherwood pumps and they all had snap rings holding the impeller on. You may be right that this part is not needed. But, it sure makes me nervous to leave parts off. I have to admit that the Jabsco/Johnson water pump on my Yanmar does not have a snap ring retainer. But, it does have a thru-bolt arrangement that does retain the impeller.

 

[Alan Gomes]

Wow, I had no idea how strongly people feel about this. Yes, OK, it does make sense that the impeller has to rub against the cover plate to maintain a seal. I have had boats with both Oberdorfer and Sherwood pumps and they all had snap rings holding the impeller on. You may be right that this part is not needed. But, it sure makes me nervous to leave parts off.

I wouldn't say that the part is not needed: It just is not needed once the pump is installed on the engine. I'm not surprised they put the clip on it to keep the shaft from sliding out the back prior to installation. If the shaft should come out of the pump it needs to be reinserted carefully so as to avoid nicking the seals and causing a leak. Better to avoid that happening in the first place.

If I had a spare pump sitting around somewhere, I might put the clip on it as a safety precaution. But as long as you keep the pump on the engine you are just fine without it.

 

[weekendrken]

Hey @STEPHEN
I’m not sure that “strongly feeling about” characterizes it properly. This isn’t about feeling strongly about an opinion, like whether Oberdorfer should or shouldn’t install the ring merely because of shipping.
This involves FACT vs bull (in this case from a mfgr,) and opinion, recommendations, or imagining, or thinking something should or shouldn’t be, has nothing to do with the veracity of the underlying FACTs.
I’d say, if there’s anything that everyone should feel strongly about, it is that we all have/understand accurate facts about every topic. No one is trying to shoot any messenger here.
Feel the love.

 

[Richard19068]

@jonelli : Tough crowd. Although I don't think the ring is necessary I appreciate your trying to get an "official" answer and sharing what you found.

 

[jonelli]

@jonelli : Tough crowd.

Nah... I was kind of hoping for this kind of response to the thread. I feel it's good for others looking for the information.
I run mine without the ring. It's a huge pain in the a$$. I've had to swap it out while out for the weekend before.
I'm glad it works fine without the ring. I was just curious what the manufacturer would say.

 

[Stu Jackson]

if you overheat and time is critical (heading for a shoal or harbor) and need to pop in a new impeller in an emergency, would it be just as "easy enough" with the snap ring as it would be without it?
Crap, where did I stash my snap ring tool?

Which is why I have a spare impeller sitting right next to a spare shaft, ready to go.

Thanks for bringing FACTS into the discussion.

 

[Stu Jackson]

ou may be right that this part is not needed. But, it sure makes me nervous to leave parts off.

I think the concept here is that the snap ring is NOT A PART OF THE PUMP or its operation. It is simply shipping material. I usually take the plastic packaging off tools before I use them...

 

[jonelli]

The reason why I even went down this rabbit hole the other day is I was reading some article in either an online boating publication or one of the ones next to my toilet and there was an article about maintenance or something, and they were talking about finding the right snap ring tool for your impeller and where to get them, because you know how important it is to have the RIGHT tool! I had already abandoned my snap ring a couple of years ago and got curious so I wrote to the IR/Oberdorfer guys to see what they would say. I already knew about everyone's thoughts on the interwebs.

 

[weekendrken]

The sad part of this is that Oberdorfer a/k/a Ingersoll Rand doesn’t know better. (We’ve always done it that way.) There’s a cost to machining the shaft and for the cut-clip and installing it.
I could think of a simple way to keep the shaft in the pump until it’s installed.
Of course, the other way for a quick replace is to keep a spare shaft/impeller ready to pop one out, the other in. And naturally there’s a benefit to have in an extra shaft aboard. Remember Murphy can stowaway.
Or if you carry an extra pump you have a cir-clipped setup ready to go.
Many options.

 

[Stu Jackson]

...doesn’t know better. (We’ve always done it that way.)

In all fairness, Ken, if I worked for the PUMP MANUFACTURER, my answer would be: "Sure, you need the clip." Because they are looking at it from THEIR POINT OF VIEW.

Darin Mountain (OBERDORFER & MP Pumps)
Mar 10, 2021, 15:34 CST
The snap ring is needed in the pump assembly. IR/Oberdorfer does not recommend running the N202 series without all of the internal components in place.

Darin Mountain
Applications Specialist

Darin answered jonelli's question. But jonelli didn't share with us what his specific question was.
It could have been as simple as: "Is the circlip necessary?" If so, Darin's answer could be quite proper, BECAUSE the question was limited, and as far as Darin is concerned, it sure IS necessary for him, so the shafts actually come along with the pumps!!!

If, however, jonelli asked, "Hey, Darin, is the clip necessary for proper PUMP OPERATION?", then Darin's answer is, at least, incomplete.

None of us was there for that conversation.

This is NOT to cast aspersions, simply to attempt to put different possibilities in perspective.

English is a shitty language for engineering.

 

[jonelli]

jonelli didn't share with us what his specific question was.

Stu, you are very right for calling me out! So, to make it as clear as possible, here is the EXACT back and forth between myself and Darin:

ME: "Is the snap ring required?? (N202 style pumps) A lot has been debated on whether we need to use the included snap rings when replacing the impellers. Some have said it is NOT needed once the pump is installed, that it is simply used for original shipping of the pump so it doesn't fall apart when not installed. Others have gone out of the way to find expensive tools to keep on board to remove and replace the snap rings. Certainly, without a tool it is tricky to replace while at sea. Can we definitively know whether or not these snap rings are required for normal use once the pump is installed? Thank you!"

DARIN: "The snap ring is needed in the pump assembly. IR/Oberdorfer does not recommend running the N202 series without all of the internal components in place."

ME: "Thanks for the reply. Just to clarify though, can you tell me what the ring accomplishes in that design? Some use it without and some use it with. Does it prevent risk of spinning? Something else?"

DARIN: "The snap ring insures proper alignment in the assembly."